What are the best Intravenous (IV) antibiotics for cat bites?

Best IV Antibiotics for Cat Bites

For cat bite infections requiring intravenous therapy, ampicillin-sulbactam (1.5-3g every 6-8 hours) is the recommended first-line treatment due to its excellent coverage of Pasteurella multocida and other common pathogens found in cat bites. 1, 2

Microbiology of Cat Bites

Cat bites have a particularly high infection rate (75%) compared to dog bites (50%) and typically involve:

• Pasteurella multocida (found in 75% of cat bites)
• Staphylococci and streptococci (found in ~40% of bites)
• Anaerobes (present in 65% of cat bites)
• Other organisms including Capnocytophaga canimorsus

First-Line IV Antibiotic Options

1. Ampicillin-sulbactam: 1.5-3g IV every 6-8 hours 1, 2

   • Provides excellent coverage against both aerobic and anaerobic organisms
   • Dosage adjustment required for renal impairment 2

2. Piperacillin-tazobactam: 3.37g IV every 6-8 hours 1

   • Broad spectrum coverage but misses MRSA

Alternative IV Options

For patients with penicillin allergies or when first-line agents are not appropriate:

1. Carbapenems (ertapenem, imipenem, meropenem) 1

   • Excellent broad-spectrum coverage
   • Misses MRSA

2. Second-generation cephalosporins (e.g., cefoxitin) 1

   • Good activity against P. multocida
   • May need additional anaerobic coverage

3. Fluoroquinolones (ciprofloxacin, levofloxacin, moxifloxacin) 1

   • Moxifloxacin (400mg daily) provides good anaerobic coverage
   • Ciprofloxacin (400mg every 12h) and levofloxacin (750mg daily) have good activity against P. multocida but may miss some anaerobes

4. Doxycycline: 100mg IV every 12 hours 1, 3

   • Excellent activity against P. multocida
   • Some streptococci may be resistant

Special Considerations

When to Use IV Antibiotics

• Rapidly spreading infection
• Systemic symptoms (fever, chills)
• Deep tissue involvement (tendons, joints, bones)
• Immunocompromised patients
• Hand infections (high risk for complications) 1, 4

Duration of Therapy

• Standard infections: 7-14 days
• Complicated infections (osteomyelitis, septic arthritis): 3-6 weeks 1

Monitoring and Follow-up

• Monitor for clinical improvement within 24-48 hours
• Consider switching to oral therapy when clinically improving
• Follow closely for potential complications like septic arthritis, osteomyelitis, or endocarditis 4, 5

Common Pitfalls to Avoid

1. Inadequate coverage of P. multocida: First-generation cephalosporins, penicillinase-resistant penicillins (dicloxacillin), macrolides, and clindamycin alone have poor activity against P. multocida and should be avoided 1

2. Premature discontinuation of antibiotics: Incomplete treatment can lead to serious complications including endocarditis 4

3. Delayed treatment: Cat bites can rapidly progress to serious infections within 12-24 hours due to the deep puncture wounds and high bacterial load 6

4. Overlooking deep structure involvement: Cat bites can penetrate deep tissues causing tenosynovitis, septic arthritis, or osteomyelitis requiring surgical intervention 5

Remember that proper wound care, including thorough irrigation and debridement if necessary, is an essential component of treatment alongside appropriate antibiotic therapy 1, 3.